I. Field
The present invention relates generally to electronic circuits, and more specifically to a digital-to-analog converter (DAC).
II. Background
DACs are widely used for various applications including wireless communication. For example, a wireless device in a wireless communication system typically employs a transmit DAC (TxDAC) to convert one or more digital data streams into one or more analog signals, which are further processed to generate a radio frequency (RF) output signal that is suitable for transmission over a wireless channel. The TxDAC is typically designed to meet stringent dynamic specifications for spurious free dynamic range (SFDR), signal-to-noise ratio (SNR), total harmonic distortion (THD), and so on. These dynamic specifications determine the quality (e.g., spectral purity) of the analog signals from the TxDAC and are normally set such that the RF output signal can meet the overall specifications imposed by the wireless system.
Most conventional TxDACs have insufficient linearity and/or an excessively high noise floor and, by themselves, cannot achieve the dynamic performance required to meet the overall wireless system specifications. As a result, the dynamic specifications for the TxDAC are often relaxed. Additional hardware is then employed after the TxDAC to further condition the analog signals and allow the RF output signal to meet the overall wireless system specifications. However, the additional hardware adds complexity, increases cost, and degrades performance for some parameters, all of which are undesirable for a wireless device.
Newer wireless communication systems often have wider operating bandwidth and support higher data rates. These systems also tend to have more stringent system specifications, which may impose more stringent dynamic requirements on the TxDAC. There is therefore a need in the art for a DAC having good dynamic performance and suitable for use as a TxDAC for wireless communication.